Taiwan Utility Model application No. 80207218 filed on Jun. 13, 1991, disclosed a stroller having a handlebar interchangeable between a forward and a backward positions with respect to the seat, with the front wheel sets thereof swivel freely while the rear wheel sets move fore and aft at random orientation when said handlebar at the forward position, and vice versa when said handlebar at the backward position. At random orientation the locking lever at fixed location on the respective wheel set is occasionally difficult to operate. In addition, said handlebar is interchanged between said positions by a wire through a block disposed inside of the support tubes of the wheel sets. When said tubes are indented or deformed inadvertently said block will be obstructed at the defect place, resulting the malfunction on the interchanging operation. Moreover, one pin to one hole engagement causes the wheel set unstable.